The present invention pertains generally to surgical devices. More particularly, the present invention pertains to surgical lenses which are used in ophthalmic laser surgery. The present invention is particularly, but not exclusively, useful as a lens for temporarily reconfiguring the cornea from an imperfect shape which causes light passing through the cornea to experience aberration into a shape that allows light to pass through the cornea with little or no aberration.
For ophthalmic laser procedures involving the photodisruption of eye tissue, it is extremely important for the laser beam to be properly focused to a spot at a prescribed location inside the tissue. To make accurate incisions with the laser, it is extremely important that the focal spot have good definition. Specifically, it is desirable that the laser beam reach the focal spot free from aberrations that can distort the definition of the focal spot.
For ophthalmic laser procedures involving the cornea, a beam of laser light is generally passed through the anterior surface of the cornea and focused within the cornea. Unfortunately, since the anterior surface of the cornea in its natural state is nearly spherical, once a beam of light passes through the anterior surface of the cornea, aberrations are introduced into the beam that cause the beam to distort. For light beams that are focused to a focal spot within the cornea, these corneal induced aberrations distort the definition of the focal spot. It follows that more accurate incisions can be performed by reducing or eliminating these corneal induced aberrations.
For light beams that are focused to a focal spot within the cornea, both spherical aberration and coma cause a loss of definition of the focal spot. Conversely, it is known that when a light beam passes through a flat interface between two mediums, no spherical aberration or coma is introduced into the beam. Similarly, when a light beam passes through a nearly flat or slightly curved interface between two mediums, the effects of spherical aberration and coma are much less pronounced than for a light beam passing through a nearly spherical interface, such as the anterior surface of the cornea. As recognized by the present invention, the effects of spherical aberration and coma on light beams passing through the anterior surface of the cornea can be reduced or eliminated by reconfiguring the anterior surface of the cornea from its nearly spherical natural shape to a flatter configuration.
Generally, no two corneas are identical. Rather, the exact shape and curvature of the anterior shape of each cornea is slightly different. Consequently, each cornea in its natural state introduces different amounts of aberration into a light beam passing through the anterior surface of the cornea. For a light beam focused to a focal spot within the cornea, the unique shape of each cornea effects the definition of the focal spot differently. The present invention recognizes that the effects of spherical aberration and coma on light beams passing through the anterior surface of the cornea can be predicted by flattening the anterior surface of the cornea against a surface of known curvature. By using a surface of known curvature, a focal spot of known definition can be obtained and this knowledge can be used to ensure the desired surgical effect.
In light of the above, it is an object of the present invention to provide a disposable lens which will reconfigure the cornea for surgical laser procedures into a configuration wherein the effects of spherical aberration and coma on a light beam passing through the anterior surface of the cornea are reduced or eliminated. Yet another object of the present invention is to provide a disposable lens which will stabilize and maintain a proper orientation of the eye during ophthalmic laser surgery. Still another object of the present invention is to provide a disposable lens which will beneficially maintain near-normal intraocular pressure during ophthalmic laser surgery. Another object of the present invention is to provide a disposable lens which is easy to use, relatively simple to manufacture and comparatively cost effective.
In one embodiment for the present invention, a lens for use in ophthalmic laser surgery includes an optical element in combination with a suction means. More specifically, the suction means is connected in fluid communication with the optical element to selectively create a partial vacuum between the optical element and the cornea when the lens is positioned over an eye. In response to the partial vacuum, the cornea is forced against the optical element. This reconfigures the cornea for laser surgery and thereby reduces or eliminates optical aberrations that would otherwise be caused by the natural shape of the cornea.
In more detail, the optical element of the present invention includes a lens member which has two opposed surfaces; a substantially flat anterior surface and a substantially flat or slightly curved contact surface. Specifically, as intended for the present invention, the contact surface can be shaped flat or slightly curved to cause the shape of the anterior surface of the cornea to change when the anterior surface of the cornea is held against the contact surface. Preferably, the lens member is made of a substantially clear, medical grade plastic. Additionally, a skirt surrounds the contact surface and extends outwardly therefrom to establish and surround a recessed chamber and define an opening to the recessed chamber. In the preferred embodiment, the skirt is formed with a sealing surface for contacting the cornea. The sealing surface of the skirt is preferably formed having a concave shape extending into the recess. The concave shape of the sealing surface allows the skirt to establish a seal with the cornea when the lens is placed against the eye. Preferably, the sealing surface of the skirt is made of a soft medical grade plastic to further facilitate a strong seal between the skirt and the cornea during use. Inside the recessed chamber, a suction channel is provided at the interface between the contact surface and the skirt.
A suction device, such as a vacuum pump or a syringe, is connected in fluid communication with the recessed chamber via the suction channel. With this combination, a partial vacuum can be created in the recessed chamber whenever the opening to the chamber is covered. Specifically, as intended for the present invention, the opening to the chamber is to be covered by the cornea, and the cornea is to be drawn into the chamber where it is flattened against the contact surface of the lens.
As intended for the present invention, the lens can be mounted on a retainer ring which is attached to the laser system that is being used. More specifically, the retainer ring holds the lens in a predetermined orientation relative to the laser system so that the laser surgery can be performed.
In the operation of the present invention, the aplanatic lens is positioned over the eye so that the cornea of the eye is covered by the opening into the recessed chamber. The suction device is then activated to create a partial vacuum in the chamber. Due to this partial vacuum, the cornea is pulled or drawn into the chamber. Specifically, the cornea is flattened against the contact surface of the optical element. As indicated above, with the flattening of the cornea, spherical aberrations and comas which would otherwise be caused by the spherical geometry of the cornea are reduced or eliminated. After the particular ophthalmic laser procedure has been completed, the suction device is deactivated, the partial vacuum is dissipated, and the aplanatic lens is removed from the eye. The lens can be discarded and another new aplanatic lens may be used for the next patient.
In another embodiment for the present invention, the lens member as described above can be used in conjunction with a skirt formed with projections for holding the skirt and lens member in position relative to the eye. In this embodiment, the skirt surrounds the contact surface of the lens member and extends outwardly therefrom to establish and surround a recessed chamber and define an opening for the chamber. A plurality of projections are provided extending from the skirt near the opening for engagement with the cornea. A mechanism is provided to attach the lens member and skirt to a laser source.